是否可以将图像保存为对象并存储在NSUserDefaults
中,以供进一步使用?
是否可以将图像保存为对象并存储在NSUserDefaults
中,以供进一步使用?
要将图像保存在NSUserDefaults中:
[[NSUserDefaults standardUserDefaults] setObject:UIImagePNGRepresentation(image) forKey:key];
从NSUserDefaults检索图像的方法:NSData* imageData = [[NSUserDefaults standardUserDefaults] objectForKey:key];
UIImage* image = [UIImage imageWithData:imageData];
注意!如果您正在使用iOS8/XCODE6,请查看下面的更新
对于那些仍在寻找答案的人,以下是“可行”的代码,用于在NSUserDefaults中保存图像。 您不应该直接将图像数据保存到NSUserDefaults中!
写入数据:
// Get image data. Here you can use UIImagePNGRepresentation if you need transparency
NSData *imageData = UIImageJPEGRepresentation(image, 1);
// Get image path in user's folder and store file with name image_CurrentTimestamp.jpg (see documentsPathForFileName below)
NSString *imagePath = [self documentsPathForFileName:[NSString stringWithFormat:@"image_%f.jpg", [NSDate timeIntervalSinceReferenceDate]]];
// Write image data to user's folder
[imageData writeToFile:imagePath atomically:YES];
// Store path in NSUserDefaults
[[NSUserDefaults standardUserDefaults] setObject:imagePath forKey:kPLDefaultsAvatarUrl];
// Sync user defaults
[[NSUserDefaults standardUserDefaults] synchronize];
读取数据:
NSString *imagePath = [[NSUserDefaults standardUserDefaults] objectForKey:kPLDefaultsAvatarUrl];
if (imagePath) {
self.avatarImageView.image = [UIImage imageWithData:[NSData dataWithContentsOfFile:imagePath]];
}
documentsPathForFileName:
- (NSString *)documentsPathForFileName:(NSString *)name {
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsPath = [paths objectAtIndex:0];
return [documentsPath stringByAppendingPathComponent:name];
}
针对iOS8/XCODE6的问题 如下方评论中所述,有一个关于xcode6/ios8的问题。xcode5和xcode6安装过程的区别在于,xcode6在每次在xcode中运行后更改应用程序UUID(请参见路径中突出显示的部分:/var/mobile/Containers/Data/Application/B0D49CF5-8FBE-4F14-87AE-FA8C16A678B1/Documents/image.jpg)。
因此,有两个解决方法:
以下是使用第二种方法的Swift代码版本(额外提供的):
写入数据:
let imageData = UIImageJPEGRepresentation(image, 1)
let relativePath = "image_\(NSDate.timeIntervalSinceReferenceDate()).jpg"
let path = self.documentsPathForFileName(relativePath)
imageData.writeToFile(path, atomically: true)
NSUserDefaults.standardUserDefaults().setObject(relativePath, forKey: "path")
NSUserDefaults.standardUserDefaults().synchronize()
读取数据:
let possibleOldImagePath = NSUserDefaults.standardUserDefaults().objectForKey("path") as String?
if let oldImagePath = possibleOldImagePath {
let oldFullPath = self.documentsPathForFileName(oldImagePath)
let oldImageData = NSData(contentsOfFile: oldFullPath)
// here is your saved image:
let oldImage = UIImage(data: oldImageData)
}
documentsPathForFileName:
func documentsPathForFileName(name: String) -> String {
let paths = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true);
let path = paths[0] as String;
let fullPath = path.stringByAppendingPathComponent(name)
return fullPath
}
NSURLIsExcludedFromBackupKey
资源值(如此处所述:https://developer.apple.com/library/ios/qa/qa1719/_index.html)。我需要它位于文档目录中,因为它必须高度持久化。你认为这样可以吗?或者你有其他推荐的位置吗? - Chris Harrison尽管可以将UIImage
保存到NSUserDefaults
中,但通常不建议这样做,因为这不是保存图像最有效的方法;更有效的方法是将图像保存在应用程序的Documents目录
中。
针对这个问题,我已经附上了答案,并提供了更有效的保存UIImage
的方法。
保存到NSUserDefaults中
该方法允许您将任何UIImage
保存到NSUserDefaults
中。
-(void)saveImageToUserDefaults:(UIImage *)image ofType:(NSString *)extension forKey:(NSString *)key {
NSData * data;
if ([[extension lowercaseString] isEqualToString:@"png"]) {
data = UIImagePNGRepresentation(image);
} else if ([[extension lowercaseString] isEqualToString:@"jpg"]) {
data = UIImageJPEGRepresentation(image, 1.0);
}
NSUserDefaults * userDefaults = [NSUserDefaults standardUserDefaults];
[userDefaults setObject:data forKey:key];
[userDefaults synchronize];
}
这是你如何称呼它的方式:[self saveImageToUserDefaults:image ofType:@"jpg" forKey:@"myImage"];
[[NSUserDefaults standardUserDefaults] synchronize];
从NSUserDefaults中读取
这种方法允许您从NSUserDefaults
中加载任何UIImage
。
-(UIImage *)loadImageFromUserDefaultsForKey:(NSString *)key {
NSUserDefaults * userDefaults = [NSUserDefaults standardUserDefaults];
return [UIImage imageWithData:[userDefaults objectForKey:key]];
}
这是如何称呼它:
UIImage * image = [self loadImageFromUserDefaultsForKey:@"myImage"];
保存到文档目录
这种方法允许你将任何UIImage
保存到应用程序内的文档目录
中。
-(void)saveImage:(UIImage *)image withFileName:(NSString *)imageName ofType:(NSString *)extension inDirectory:(NSString *)directoryPath {
if ([[extension lowercaseString] isEqualToString:@"png"]) {
[UIImagePNGRepresentation(image) writeToFile:[directoryPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", imageName, @"png"]] options:NSAtomicWrite error:nil];
} else if ([[extension lowercaseString] isEqualToString:@"jpg"] || [[extension lowercaseString] isEqualToString:@"jpeg"]) {
[UIImageJPEGRepresentation(image, 1.0) writeToFile:[directoryPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", imageName, @"jpg"]] options:NSAtomicWrite error:nil];
} else {
NSLog(@"Image Save Failed\nExtension: (%@) is not recognized, use (PNG/JPG)", extension);
}
}
这就是如何称呼它:
NSString * documentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
[self saveImage:image withFileName:@"Ball" ofType:@"jpg" inDirectory:documentsDirectory];
从文档目录加载
该方法允许您从应用程序的文档目录
加载任何UIImage
。
-(UIImage *)loadImageWithFileName:(NSString *)fileName ofType:(NSString *)extension inDirectory:(NSString *)directoryPath {
UIImage * result = [UIImage imageWithContentsOfFile:[NSString stringWithFormat:@"%@/%@.%@", directoryPath, fileName, [extension lowercaseString]]];
return result;
}
这是如何称呼它:
NSString * documentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
UIImage * image = [self loadImageWithFileName:@"Ball" ofType:@"jpg" inDirectory:documentsDirectory];
将UIImage保存到照片库
此方法允许您将任何UIImage
保存到设备的照片库
中,并按以下方式调用:
UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);
保存多张UIImage到相册
这个方法允许您将多张UIImages
保存到设备的相册
中。
-(void)saveImagesToPhotoAlbums:(NSArray *)images {
for (int x = 0; x < [images count]; x++) {
UIImage * image = [images objectAtIndex:x];
if (image != nil) UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);
}
}
这是如何称呼它:
[self saveImagesToPhotoAlbums:images];
其中images
是由UIImages
组成的NSArray
。
inDirectory: (NSString *)directoryPath
- 你可以随便取一个名字,比如“myAppData”吗? - Supertecnoboff针对Swift 4
我尝试了这个问题中几乎所有的方法,但没有一个适用于我。最终,我找到了解决方案。 首先我创建了一个UserDefaults的扩展,如下所示,然后只需调用get和set方法。
extension UserDefaults {
func imageForKey(key: String) -> UIImage? {
var image: UIImage?
if let imageData = data(forKey: key) {
image = NSKeyedUnarchiver.unarchiveObject(with: imageData) as? UIImage
}
return image
}
func setImage(image: UIImage?, forKey key: String) {
var imageData: NSData?
if let image = image {
imageData = NSKeyedArchiver.archivedData(withRootObject: image) as NSData?
}
set(imageData, forKey: key)
}
}
我使用下面的代码将图像设置为SettingsVC的背景。
let croppedImage = cropImage(selectedImage, toRect: rect, viewWidth: self.view.bounds.size.width, viewHeight: self.view.bounds.size.width)
imageDefaults.setImage(image: croppedImage, forKey: "imageDefaults")
在 mainVC 中:
let bgImage = imageDefaults.imageForKey(key: "imageDefaults")!
针对 Swift 2.2 版本
存储:
NSUserDefaults.standardUserDefaults().setObject(UIImagePNGRepresentation(chosenImage), forKey: kKeyImage)
要检索:
if let imageData = NSUserDefaults.standardUserDefaults().objectForKey(kKeyImage),
let image = UIImage(data: imageData as! NSData){
// use your image here...
}
[[NSUserDefaults standardUserDefaults] setObject:UIImagePNGRepresentation(image) forKey:@"foo"];
但是不建议在plist文件中存储大量的二进制数据,特别是用户偏好设置。最好将图像保存到用户文档文件夹中,并将该对象的引用作为URL或路径存储。
针对 Swift 3 和 JPG 格式:
注册默认图像:
UserDefaults.standard.register(defaults: ["key":UIImageJPEGRepresentation(image, 100)!])
保存图像:
UserDefaults.standard.set(UIImageJPEGRepresentation(image, 100), forKey: "key")
加载图片:
let imageData = UserDefaults.standard.value(forKey: "key") as! Data
let imageFromData = UIImage(data: imageData)!
从苹果文档中获得的信息:
NSUserDefaults类提供了方便的方法来访问常见类型,例如floats、doubles、integers、Booleans和URLs。默认对象必须是属性列表,也就是NSData、NSString、NSNumber、NSDate、NSArray或NSDictionary的实例(对于集合则是实例的组合)。如果您想存储任何其他类型的对象,则通常应将其归档以创建NSData的实例。
您可以像这样保存图像:
[[NSUserDefaults standardUserDefaults] setObject:UIImagePNGRepresentation([UIImage imageNamed:@"yourimage.gif"])forKey:@"key_for_your_image"];
请按如下方式阅读:
NSData* imageData = [[NSUserDefaults standardUserDefaults]objectForKey:@"key_for_your_image"];
UIImage* image = [UIImage imageWithData:imageData];
从技术上讲,这是可能的,但不建议这样做。相反,应该将图像保存到磁盘中。NSUserDefaults适用于小型设置,而不是大型二进制数据文件。
将图像保存到 NSUserDefaults:
NSData *imageData;
// create NSData-object from image
imageData = UIImagePNGRepresentation([dic objectForKey:[NSString stringWithFormat:@"%d",i]]);
// save NSData-object to UserDefaults
[[NSUserDefaults standardUserDefaults] setObject:imageData forKey:[NSString stringWithFormat:@"%d",i]];
从 NSUserDefault 中加载图像:
NSData *imageData;
// Load NSData-object from NSUserDefault
imageData = [[NSUserDefaults standardUserDefaults] valueForKey:[NSString stringWithFormat:@"%d",i]];
// get Image from NSData
[image setObject:[UIImage imageWithData:imageData] forKey:[NSString stringWithFormat:@"%d",i]];